Conventionally, it is proposed to utilize a hybrid vehicle or an electric vehicle having a motor generator as a motive power source as a commercial power source (for example, see Japanese Patent Laying-Open Nos. 2001-258177, 2001-008380, and 04-295202). The idea is to utilize a hybrid vehicle or the like as an emergency power source in an emergency or disaster, or as a commercial power source at a camp site or the like where there is no commercial power supply equipment around.
For example, Japanese Patent Laying-Open No. 2001-258177 discloses an AC power supplying system that supplies power from a battery mounted on an electric vehicle to a domestic power supply in a house. Specifically, with provision of a charger/discharger connected to a power line on the house side and a controller controlling charge/discharge by monitoring the state of the battery mounted on an electric vehicle, it is possible to realize both of power supply from the household power supply to the electric vehicle and power supply from the electric vehicle to the household power supply. Further, when supplying power from the electric vehicle to the house side, an amount of power required for the electric vehicle to run within a normal traveling range is secured to allow for urgent outing.
With a conventional AC power supplying system, however, the following problems would occur when AC power is supplied to an external electric load from a vehicle instead of a commercial power source.
In a conventional system, when the commercial power source is normal and is capable of supplying power to an electric load, approximately constant AC power with high output level is supplied to the electric load. When power is supplied from the commercial power source to a plurality of electric loads placed in a house, the power supply is shut off by a breaker when the load amount of the electric loads exceeds the level permitted to the consumer of electricity under contract.
Upon power failure of the commercial power source, hindering power supply therefrom, power supply is switched to the vehicle as an emergency power source. At this time, the AC power output from the vehicle varies depending on the state of the power supply apparatus generating the AC power and the like. As such, it is difficult to supply power to the electric loads as stably as in the case of using the commercial power source.
For example, assume that the AC power output from the vehicle is less than the AC power output from the commercial power source. In this case, on the house side, while the load amount of the electric loads before and after the power failure is constant, the supply amount of the AC power decreases. At this time, if power is being supplied from the commercial power source, the breaker will shut off the power supply, as described above, because the load amount exceeds the supply amount of the AC power. In contrast, in the case of supplying power from the vehicle, the breaker will not shut off the power supply, and thus, the AC voltage output from the power supply apparatus will suffer considerable voltage drop.
Taking into consideration such drop of the AC voltage, in the conventional system, the electric loads to be used by the consumer of electricity would be restricted in advance, before switching the power source from the commercial power source to the power supply apparatus of the vehicle. This means that in an emergency like power failure of the commercial power source, the power source cannot be switched automatically.
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an AC power supplying system capable of restricting drop of an AC voltage output from a power supply apparatus, a power supply apparatus, and a vehicle having the same.